pH-Responsive Protein Conjugates for Intracellular Delivery
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for delivering biologic therapeutic agents to intracellular targets face challenges such as endosomal escape and biodistribution issues due to positive charge modifications, which lead to instability and reduced efficacy.
Innovation Solution
Development of protein conjugates with a biological payload covalently bound to a cell-penetrating moiety, where at least a portion of the amine groups are bound to a protecting group capable of cleavage at a pH less than 7, resulting in a negative zeta potential and improved blood stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If protein-based therapeutic agents are modified with highly positively charged polymers (e.g., PEI) to enhance cell penetration, then intracellular delivery efficiency is improved, but blood stability and biodistribution are worsened due to adhesion with negatively charged blood components
Solution Approach 1:
The patent applies preliminary action by pre-modifying the protein therapeutic agent with a polyethyleneimine (PEI) polymer before administration. This preliminary modification enables the agent to acquire cell-penetrating capabilities in advance, while the subsequent pH-responsive masking mechanism ensures blood stability is maintained until the agent reaches its target. The PEI modification is performed beforehand to establish the foundation for intracellular delivery without immediately causing blood adhesion issues.
Solution Approach 2:
The patent utilizes parameter changes by employing a pH-responsive masking mechanism that alters the charge state of the PEI-modified protein agent. At physiological pH (blood conditions), the amine groups of PEI are masked, rendering the agent neutral or negatively charged to prevent blood adhesion. Upon endosomal escape into the cytoplasm, the masking is removed and the agent becomes positively charged to facilitate membrane interaction and intracellular delivery. This dynamic parameter change resolves the contradiction between blood stability and intracellular delivery efficiency.
2Ease of operation
If protein-based therapeutic agents are delivered via natural endocytosis to enter living cells, then cellular internalization is achieved, but the agents are directed to lysosomal degradation rather than reaching intracellular targets
Solution Approach 1:
The patent applies the blessing in disguise principle by converting the harmful lysosomal degradation pathway into a beneficial delivery route. The PEI-modified protein agent is deliberately designed to be internalized via endocytosis, which normally leads to lysosomal degradation. However, the pH-responsive masking mechanism exploits the acidic environment of endosomes and lysosomes to trigger masking removal, enabling the agent to escape from these compartments and reach the cytoplasm. Thus, the previously harmful endosomal pathway becomes a useful vehicle for delivering the therapeutic agent to its intended intracellular target.
Solution Approach 2:
The patent utilizes parameter changes by exploiting the pH gradient between different cellular compartments. The masking mechanism is designed to be stable at neutral pH (cytoplasm) but removable at acidic pH (endosomes/lysosomes). This parameter change allows the agent to navigate through the endosomal pathway, undergo masking removal in the acidic environment, and subsequently escape to the cytoplasm where the masking is stable again. This dynamic pH-responsive behavior converts the lysosomal degradation pathway into a delivery route to the cytoplasm.
3Reliability
If the therapeutic biologic is released into the cytoplasm after endosomal escape, then intracellular target access is enabled, but the crowded cytoplasmic environment reduces therapeutic agent dispersion and target engagement efficiency
Solution Approach 1:
The patent applies the taking out principle by extracting the masking groups from the PEI-modified protein agent upon reaching the cytoplasm. This extraction of masking enables the agent to adopt its active conformation and engage with intracellular targets. The masking removal also facilitates the agent's dispersion in the cytoplasmic environment by reducing steric hindrance and improving solubility, thereby enhancing target engagement efficiency despite the crowded cytoplasmic conditions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The protein conjugates demonstrate enhanced blood stability and accumulation in tissues with acidic pH, facilitating effective intracellular delivery and targeting of therapeutic agents.
Implementation Method 1
at least a portion of the amine groups is bound to a protecting group capable of undergoing cleavage at a pH value of less than 7
Implementation Method 2
The protein conjugates demonstrate enhanced blood stability and accumulation in tissues with acidic pH, facilitating effective intracellular delivery
Data Source
AI summary
Protein conjugates comprising a protein carrier comprising a plurality of amine groups, a biological payload that interacts with an intracellular target and a linker linking them, wherein at least a portion of the amine groups are bound to a protecting group are provided. Pharmaceutical compositions comprising the protein conjugates as well as methods of using and producing the protein conjugates are also provided.